Light emitting devices with built-in chromaticity conversion and methods of manufacturing

ABSTRACT

Various embodiments of light emitting devices with built-in chromaticity conversion and associated methods of manufacturing are described herein. In one embodiment, a method for manufacturing a light emitting device includes forming a first semiconductor material, an active region, and a second semiconductor material on a substrate material in sequence, the active region being configured to produce a first emission. A conversion material is then formed on the second semiconductor material. The conversion material has a crystalline structure and is configured to produce a second emission. The method further includes adjusting a characteristic of the conversion material such that a combination of the first and second emission has a chromaticity at least approximating a target chromaticity of the light emitting device.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.14/874,231 filed Oct. 2, 2015, which is a divisional of U.S. patentapplication Ser. No. 14/489,344 filed Sep. 17, 2014, now U.S. Pat. No.9,184,336, which is a divisional of U.S. patent application Ser. No.13/116,366 filed May 26, 2011, now U.S. Pat. No. 8,847,198, each ofwhich is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure is related to light emitting devices withbuilt-in chromaticity conversion and associated methods ofmanufacturing.

BACKGROUND

Light emitting diodes (“LEDs”) and other types of light emitting devicesare widely used for background illumination in electronic devices andfor signage, indoor lighting, outdoor lighting, and other types ofgeneral illumination. Light emitting devices typically emit light atonly one center wavelength, and thus they do not produce white light.One conventional technique for emulating white light with LEDs includesdepositing a phosphor on an LED die. FIG. 1A shows a conventional lightemitting device 10 that has a support 2, an LED die 4, and a phosphor 6.FIG. 1B shows an example of an LED die 4 that includes a substrate 12,an N-type gallium nitride (GaN) material 14, GaN/indium gallium nitride(InGaN) multiple quantum wells (“MQWs”) 16, a P-type GaN material 18, afirst contact 20, and a second contact 22.

Referring to both FIGS. 1A and 1B, in operation, an electrical voltageis applied between the first and second contacts 20 and 22. In responseto the applied voltage, the MQWs 16 of the LED die 4 produce a firstemission (e.g., a blue light) that stimulates the phosphor 6 to emit asecond emission (e.g., a yellow light). The combination of the first andsecond emissions appears generally white to human eyes if matchedappropriately. As discussed in more detail below, using phosphors hascertain drawbacks. Accordingly, several improvements in modifyingemission of light emitting devices without using phosphors may bedesirable.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic cross-sectional diagram of a light emittingdevice in accordance with the prior art.

FIG. 1B is a schematic cross-sectional diagram of an LED die inaccordance with the prior art.

FIG. 2A is a schematic cross-sectional diagram of a light emittingdevice with built-in chromaticity conversion in accordance withembodiments of the technology.

FIG. 2B is a schematic cross-sectional diagram of a light emittingdevice with built-in chromaticity conversion in accordance withadditional embodiments of the technology.

FIG. 2C is a schematic cross-sectional diagram of a light emittingdevice with built-in chromaticity conversion in accordance with furtherembodiments of the technology.

FIG. 3A is a schematic cross-sectional diagram of a conversion materialuseful for the light emitting device in FIGS. 2A-2C in accordance withembodiments of the technology.

FIG. 3B is a schematic cross-sectional diagram of a conversion materialuseful for the light emitting device in FIGS. 2A-2C in accordance withadditional embodiments of the technology.

FIG. 4 is a flowchart illustrating a method for forming embodiments ofthe light emitting devices in FIGS. 2A-2C in accordance with embodimentsof the technology.

FIGS. 5A and 5B are chromaticity plots of examples of combined emissionfrom an LED die with a conversion material in accordance withembodiments of the technology.

DETAILED DESCRIPTION

Various embodiments of light emitting devices with built-in chromaticityconversion and associated methods of manufacturing are described below.As used hereinafter, the term “light emitting device” generally refersto LEDs, laser diodes, and/or other suitable sources of illuminationother than electrical filaments, a plasma, or a gas. The term“chromaticity” generally refers to an objective specification of thequality of a color regardless of the luminance of the color.Chromaticity of the color may be determined by hue, colorfulness,saturation, chroma, intensity, and/or excitation purity. A personskilled in the relevant art will also understand that the technology mayhave additional embodiments, and that the technology may be practicedwithout several of the details of the embodiments described below withreference to FIGS. 2A-6.

FIG. 2A is a schematic cross-sectional diagram of a light emittingdevice 100 with built-in chromaticity conversion in accordance withembodiments of the technology. As shown in FIG. 2A, the light emittingdevice 100 can include a substrate material 112, an optional buffermaterial 113, a first semiconductor material 114, an active region 116,and a second semiconductor material 118. The light emitting device 100also has a built-in conversion material 120 on or at least proximate thesecond semiconductor material 118. Even though only one conversionmaterial 120 is shown in FIG. 2A for illustration purposes, in otherembodiments, the light emitting device 100 may include two, three, four,or any other suitable number of conversion materials 120 or layers ofconversion materials with different emission center wavelengths and/orother characteristics. In further embodiments, the light emitting device100 can optionally include a reflective material (e.g., a silver film),a carrier material (e.g., a ceramic substrate), an optical component(e.g., a collimator), and/or other suitable components.

In the illustrated embodiment, the light emitting device 100 alsoincludes a first contact 102 laterally spaced apart from a secondcontact 104 (e.g., gold/nickel contacts). The first contact 102 is onthe first semiconductor material 104. The second contact 104 includes afirst portion 104 a on the conversion material 120 and a second portion104 b located in a via 105 that extends between the first portion 104 aand the second semiconductor material 108. In other embodiments, thelight emitting device 100 can also have a vertical, a buried, and/orother suitable types of contact configuration.

In certain embodiments, the substrate material 112 can be a growthsubstrate for forming the first semiconductor material 114, the activeregion 116, and the second semiconductor material 118. For example, thesubstrate material 112 can include silicon (Si), at least a portion ofwhich has the Si(1,1,1) crystal orientation, silicon with other crystalorientations (e.g., Si(1,0,0)), A1GaN, GaN, silicon carbide (SiC),sapphire (Al₂O₃), zinc oxide (ZnO), a combination of the foregoingmaterials and/or other suitable substrate materials. In the illustratedembodiment, the substrate material 112 has a generally planar surface111 proximate to the optional buffer material 113. In other embodiments,the substrate material 112 may also include a non-planar surface (e.g.,having openings, channels, and/or other surface features, not shown).The substrate material 112 can alternatively be a separate supportmember that is attached to the semiconductor materials. In theseapplications, the substrate material can be made from a dielectricmaterial, conductive material, and/or semiconductive material.

Referring to FIG. 2A, the optional buffer material 113 is configured tofacilitate the formation of the first and second semiconductor materials114 and 118 and the active region 116 on the substrate material 112. Theoptional buffer material 113 can include at least one of aluminumnitride (AlN), aluminum-gallium nitride (AlGaN), zinc nitride (ZnN),GaN, and/or other suitable materials. In other embodiments, the optionalbuffer material 113 may be omitted, and the first semiconductor material104 may be formed directly on the surface 111 of the substrate material112. In yet further embodiments, other intermediate materials (e.g.,zinc oxide (ZnO)) may be formed on the substrate material 112 inaddition to or in lieu of the buffer material 113.

The first and second semiconductor materials 114 and 118 can beconfigured as cladding structures for the active region 116. In certainembodiments, the first semiconductor material 114 can include an N-typeGaN material (e.g., doped with silicon (Si)), and the secondsemiconductor material 118 can include a P-type GaN material (e.g.,doped with magnesium (Mg)). In other embodiments, the firstsemiconductor material 114 can include a P-type GaN material, and thesecond semiconductor material 118 can include an N-type GaN material. Infurther embodiments, the first and second semiconductor materials 114and 118 can individually include at least one of gallium arsenide(GaAs), aluminum gallium arsenide (AlGaAs), gallium arsenide phosphide(GaAsP), gallium(III) phosphide (GaP), zinc selenide (ZnSe), boronnitride (BN), AlGaN, and/or other suitable semiconductor materials.

The active region 116 can include a single quantum well (“SQW”), MQWs,and/or a bulk semiconductor material. As used hereinafter, a “bulksemiconductor material” generally refers to a single grain semiconductormaterial (e.g., InGaN) with a thickness greater than about 10 nanometersand up to about 500 nanometers. In certain embodiments, the activeregion 116 can include an InGaN SQW, InGaN/GaN MQWs, and/or an InGaNbulk material. In other embodiments, the active region 116 can includealuminum gallium indium phosphide (AlGaInP), aluminum gallium indiumnitride (AlGaInN), and/or other suitable materials or configurations.

The conversion material 120 can comprise a semiconductor material formedon the second semiconductor material 118 and configured to produce asecond emission stimulated by the first emission via photoluminescence.In one embodiment, the conversion material 120 may include an epitaxialbulk material (e.g., GaN) with one or more dopants 123 (FIG. 3A)introduced via doping, ion implantation, deposition, and/or othersuitable techniques, as described in more detail below with reference toFIG. 3A. The dopants 123 can include at least one of lanthanum (La),cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm),samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium(Dy), holmium (Ho), erbium (Er), thullium (Tm), ytterbium (Yb), and/orother suitable compositions. In other embodiments, the dopants 123 canalso include nanodots and/or other suitable structures.

In other embodiments, the conversion material 120 can include asuperlattice structure with a particular bandgap energy. Examples ofsuch superlattice structure include mercury telluride (HgTe)/cadmiumtelluride (CdTe), gallium arsenide (GaAs)/aluminum gallium arsenide(AlGaAs), and/or other suitable types of superlattice structures. Oneexample of a superlattice structure is described in more detail belowwith reference to FIG. 3B.

In further embodiments, the conversion material 120 can include AlGaInP,AlGaInN, and/or other suitable semiconductor materials configured asSQW, MQWs, and/or a bulk material. In yet further embodiments, theconversion material 120 can include a combination of the foregoingstructures and/or compositions. In any of the foregoing embodiments, thefirst semiconductor material 114, the active region 116, the secondsemiconductor material 118, the buffer material 113, and the conversionmaterial 120 can be formed on the substrate material 112 via metalorganic chemical vapor deposition (“MOCVD”), molecular beam epitaxy(“MBE”), liquid phase epitaxy (“LPE”), hydride vapor phase epitaxy(“HVPE”), and/or other suitable epitaxial growth techniques.

The second emission produced by the conversion material 120 may beselected based on a target chromaticity of the light emitting device100. For example, the second emission may have a particular chromaticitysuch that a combination of the first and second emissions appears whiteto human eyes. In other examples, the combination of the first andsecond emissions may have another target chromaticity. In any of theforegoing examples, combining the second emission with the firstemission may modify, impact, and/or otherwise influence the outputchromaticity of the light emitting device 100.

In one embodiment, the second emission and corresponding conversionmaterial 120 may be selected based on empirical data. For example,calibration tests may be carried out to test the chromatographicproperties of the combined emissions. In other embodiments, the secondemission and corresponding conversion material 120 may be selected basedon the bandgap energies of the active region 116 and/or the conversionmaterial 120. In further embodiments, the selection may be based on acombination of the foregoing techniques and/or other suitabletechniques. One example of a selection technique is described in moredetail below with reference to FIGS. 5A and 5B.

In operation, an electrical voltage applied between the first and secondcontacts 102 and 104 causes an electrical current (not shown) to flowbetween the first and second contacts 102 and 104 via the firstsemiconductor material 114, the active region 116, and the secondsemiconductor material 118. In response to the applied voltage andresulting current, the active region 116 produces the first emission(e.g., a blue light). The conversion material 120 then absorbs at leasta portion of the first emission and produces the second emission (e.g.,a yellow light). The combined first and second emissions with certaindesired characteristics (e.g., appearing white or another color to humaneyes) are then emitted to an external environment.

Several embodiments of the light emitting device 100 are expected toproduce white light with increased optical efficiency compared toconventional devices that use phosphors. For example, the opticalefficiency of the light emitting device 10 in FIG. 1A is rather lowbecause the phosphor 6 (FIG. 1A) absorbs a portion of the first emissionfrom the LED die 4 in order to produce the second emission. The phosphor6, for example, typically converts only about 50% to 60% of the absorbedfirst emission to the second emission. As a result, about 40% to 50% ofthe absorbed first emission is lost to heat that must be dissipated. Incontrast, embodiments of the conversion material 120 can convert about80% to about 90% of the absorbed first emission. Accordingly, the lightemitting device 100 with the conversion material 120 can achieve higheroptical efficiencies and produce less heat than conventionalphosphor-based devices.

Embodiments of the light emitting device 100 can also produce whitelight with increased reliability and longer useful life as compared toconventional devices that have a phosphor with a luminescencecomposition (e.g., Cerium(III)-doped Yttrium Aluminum garnet) in amatrix substrate (e.g., a silicone elastomer). It has been observed thatboth the luminescence composition and the matrix substrate can degradeover time when exposed to the high junction temperatures of LED dies dueat least in part to oxidation, depolymerization, crystal latticerearrangement, and/or other chemical/mechanical mechanisms. As a result,conventional devices with phosphors tend to become less reliable overtime. Accordingly, by eliminating phosphors, the light emitting device100 can have increased reliability and a longer, more useful life.

Further, embodiments of the light emitting device 100 can be lesscomplicated to manufacture and have lower costs compared to conventionaldevices. In conventional devices, both the amount, shape, and thecomposition of the phosphor must be precisely controlled to achieve thedesired emission characteristic. For example, the phosphor can havedifferent light emitting properties that range between a central regionand a peripheral region of a conventional LED die because of temperaturedifferences of these regions. Thus, the deposition of the phosphor mustbe precisely controlled to achieve consistent light emitting properties.Such precise deposition control adds complexity and higher costs to themanufacturing process. In contrast, embodiments of the light emittingdevice 100 can be readily formed on a wafer level via MOCVD, MBE, LPE,HVPE, atomic layer deposition, and/or other suitable epitaxial growthtechniques. As a result, a large number of light emitting devices (notshown) may be produced at once, and thus the process can be lesscomplicated and more cost effective than conventional techniques.

Even though the second contact 104 is shown in FIG. 2A as extendingthrough the conversion material 120, in other embodiments, theconversion material 120 can have other configurations. For example, asshown in FIG. 2B, the conversion material 120 can include a plurality ofvias 105, and the second contact 104 includes a first portion 104 aexternal to the vias 105 and a second portion 104 b in the vias 105. Asshown in FIG. 2B, the first portion 104 a covers substantially theentire surface area of the conversion material 120. In such embodiments,the second contact 104 can include indium tin oxide, zinc oxide,fluorine-doped tin oxide, antimony tin oxide, and/or other suitabletransparent conductive materials.

The conversion material 120 can also include other suitable structuralfeatures. For example, as shown in FIG. 2C, the conversion material 120can be interrupted by having a plurality of gaps 124. In one embodiment,the gaps 124 may be filled with nitrogen (N₂), argon (Ar), and/or othersuitable gases. In other embodiments, the gaps 124 may be filled with asemi-transparent or transparent material (e.g., silicon oxide) liquid orsolid material. In further embodiments, the conversion material 120 mayalso include channels, surface roughness, and/or other suitablestructure features.

In certain embodiments, the structural features of the conversionalmaterial 120 may also be adjusted to achieve a target luminance patternfor the light emitting device 100. For example, even though the gaps 124are shown in FIG. 2C as generally similar in size and spacing, incertain embodiments, the gaps 124 may have different sizes, shapesand/or spacing in different areas of the conversion material 120. Thus,the intensity values of the second emission produced from the differentareas of the conversion material 120 may differ. As a result, the lightemitting device 100 may produce different chromaticity values fromdifferent areas of the conversion material 120.

FIG. 3A is a schematic cross-sectional diagram of a conversion material120 useful for the light emitting device 100 in FIGS. 2A-2C inaccordance with embodiments of the technology. In one embodiment, theconversion material 120 can include an epitaxial bulk material 121(e.g., GaN) with one or more dopants 123 that are formed via doping, ionimplantation, deposition, and/or other suitable doping techniques. Inother embodiments, the conversion material 120 can also include apolycrystalline material with the one or more dopants 123. In furtherembodiments, the conversion material 120 may also include an optionalbuffer (e.g., zinc oxide (ZnO), not shown) proximate the secondsemiconductor material 118 (FIG. 2A).

In certain embodiments, the dopants 123 may be introduced onto a surfaceof the epitaxial bulk material 121 and subsequently annealed to achievea target penetration depth and/or density in the epitaxial bulk material121. The dopants 123 may be distributed generally evenly in theepitaxial bulk material 121, or the dopants 123 may have a density orconcentration gradient along at least one dimension of the epitaxialbulk material 121. In further embodiments, the dopants 123 may bedistributed generally evenly in a first area and may have a differentdensity or concentration gradient in a second area of the epitaxial bulkmaterial 121. In yet further embodiments, the dopants 123 may beintroduced via other suitable techniques and/or may have other suitablecomposition profiles.

FIG. 3B is a schematic cross-sectional diagram of a conversion material120 that has a superlattice structure and corresponding bandgap diagramin accordance with additional embodiments of the technology. As shown inFIG. 3B, the conversion material 120 can include a plurality ofalternating first and second compositions 126 and 128. The firstcomposition 126 can have a first bandgap that is larger than the secondbandgap of the second composition 128. As a result, charge carriers(e.g., electrons and holes) are more likely to be restricted in theindividual second compositions 128 and intra-composition transport maybe limited.

In certain embodiments, the composition and/or thickness of the firstand/or second compositions 126 and 128 may be adjusted based on thetarget chromaticity of the light emitting device 100 (FIG. 2A). Forexample, in one embodiment, the first and/or second bandgaps may beselected based on the wavelength of the target emission from theconversion material 120. In other embodiments, the thickness of thefirst and/or second compositions 126 and 128 may be adjusted to vary theintra-composition charge carrier transport. In further embodiments,other suitable characteristics of the superlattice structure may beadjusted in addition to or in lieu of the foregoing parameters.

FIG. 4 is a flowchart illustrating a method 200 for forming embodimentsof the light emitting device 100 in FIGS. 2A-2C in accordance withembodiments of the technology. The method 200 includes determining thetarget chromaticity for the light emitting device 100 (block 202). Inone embodiment, the target chromaticity is white light at ambienttemperatures. In other embodiments, the target chromaticity can haveother suitable values.

The method 200 can also include determining the emission characteristicsof the first emission from the active region (block 204). For example, acenter emission wavelength (or frequency) of the first emission may bedetermined, or the chromaticity value of the first emission may bedetermined. In further embodiments, a combination of the foregoingcharacteristics and/or other suitable characteristics of the firstemission may be determined.

The method 200 can further include determining the conversioncharacteristics for the conversion material 120 (block 205). In oneembodiment, the process may be recursive. For example, the chromaticityvalue for the second emission from the conversion material 120 may beestimated based on previously collected data and/or other suitablesources, and then the combined chromaticity value may be calculatedand/or tested via experimentation by combining the chromaticity valuesof the first and second emissions. An error between the targetchromaticity value and the current value of the combined chromaticityvalue may be generated. The error can then be used to modify theestimated chromaticity value for the second emission. The foregoingprocess is repeated until the error is within an acceptable range. Inother embodiments, the conversion characteristics for the conversionmaterial 120 may be determined with non-recursive and/or other suitabletypes of processes.

The method 200 also can include an assessment of whether there is asolution of the conversion characteristics (block 206). If a solution isfound, the process proceeds by forming the conversion material 120 viaMOCVD, MBE, LPE, HYPE, and/or other suitable epitaxial growth techniques(block 208). If a solution is not found, the process reverts to furtherdetermining the conversion characteristics for the conversion material120 at block 205.

FIGS. 5A and 5B contain chromaticity plots of examples of combined firstand second emissions in accordance with embodiments of the technology.For illustration purposes, the chromaticity plots are based onInternational Commission on Illumination (CIE) 1931 color space, thoughother types of color spaces (e.g., RGB color space) may also be used. InFIG. 5A one conversion material is illustrated, and in FIG. 5B twoconversion materials are illustrated. In other embodiments, three, four,or any other desired number of conversion materials may be used.

As shown in FIGS. 5A and 5B, the chromaticity plot 130 includes agenerally parabolic curve (commonly referred to as a spectral locus 132)and a black body curve 134 inside the spectral locus 132. The black bodycurve 134 may be defined by Planck's law as follows:

${{I\left( {v,T} \right)}{dv}} = {\left( \frac{2\; {hv}^{3}}{c^{2}} \right)\frac{1}{^{\frac{hv}{kT}} - 1}{dv}}$

where I(v,T)dv is an amount of energy emitted in the frequency rangebetween v and v+dv by a black body at temperature T; h is the Planckconstant; c is the speed of light in a vacuum; k is the Boltzmannconstant; and v is the frequency of electromagnetic radiation.

Without being bound by theory, it is believed that an average observerperceives the color white when the (x, y) color coordinates of anemission fall on or at least in the vicinity of the black body curve 134for a given temperature range (e.g., 2,000° K to about 10,000° K). It isalso believed that if one chooses any two points of color on thechromaticity plot 130, then all the colors that lie in a straight linebetween the two points can be formed or at least approximated by mixingthose two colors. Also, all of the colors that can be formed or at leastapproximated by mixing three sources are found inside a triangle formedby the source points on the chromaticity plot 130.

Based on the foregoing understanding, the operator and/or a controller(not shown) can select a conversion material to at least approximatelymatch the first emission from the active region 116 (FIG. 2A) of thelight emitting device 100 (FIG. 2A). One example of using a singleconversion material 120 is shown in FIG. 5A. As shown in FIG. 5A, theactive region 116 has a first emission peak 138 a at least proximate toabout 478 nm on the spectral locus 132. If the light emitting device 100operates at about 4,000° K, an average person would perceive the colorwhite at a black body emission point 136 near (0.38, 0.38) on thechromaticity plot 130. Thus, for the first emission, drawing a linebetween the first emission peak 138 a and the black body emission point136 would yield a conversion wavelength of about 579 nm. As a result, ifa conversion material 120 that emits a wavelength or wavelengths of 579nm is formed on the second semiconductor material 118 (FIG. 2A), theresulting combined first and second emissions would be close to or atleast approximate true white light based on the black body curve 134. Ifa second emission peak 138 b is at least proximate to about 456 nm,however, a conversion wavelength 139 b of about 586 nm would be needed.

FIG. 5B illustrates another example where two conversion materials 120are used to match the emission of the active region 116. As shown inFIG. 5B, the active region 116 has an emission point 138 at leastproximate to about 478 nm. First and second conversion materials 120have a first conversion emission point 139 a and a second conversionemission point 139 b, respectively. Thus, the emission point 138 of theactive region 116 and the first and second conversion emission points139 a and 139 b form a triangle 142 that encompasses a black bodyemission point 136 for 4,000° K. As a result, combining the foregoingemissions would yield an emission that is at least approximate to ablack body curve 134. In one embodiment, the combination of the firstand second conversion materials 120 may be determined empirically. Inother embodiments, the ratio and/or other characteristics of the firstand second conversion materials 120 may be determined based on suitablecolor correction formulas.

In any of the embodiments discussed above with reference to FIGS. 5A and5B, the operator and/or the controller can also select a thicknessand/or a density of the conversion material 120 to achieve a targetratio (referred to as “absorption ratio” hereinafter) of absorbed tonon-absorbed first emission based on the target chromaticity. Theabsorption ratio is believed to at least influence the chromaticity ofthe combined first and second emissions. Without being bound by theory,it is believed that larger thicknesses and/or higher densities of theconversion material 120 can result in higher absorption ratio of thefirst emission than smaller thicknesses and/or lower densities. As aresult, the operator and/or the controller can select a thickness and/ordensity of the conversion material 120 based on, for example, empiricaldata and/or other suitable criteria to achieve a target absorptionratio.

From the foregoing, it will be appreciated that specific embodiments ofthe technology have been described herein for purposes of illustration,but that various modifications may be made without deviating from thedisclosure. In addition, many of the elements of one embodiment may becombined with other embodiments in addition to or in lieu of theelements of the other embodiments. Accordingly, the disclosure is notlimited except as by the appended claims.

I/we claim:
 1. A method for manufacturing a light emitting device,comprising: forming a first semiconductor material, an active region,and a second semiconductor material on a substrate material in sequence,the active region being configured to produce a first emission viaelectroluminescence; determining a conversion characteristic of a secondemission based on a target chromaticity and the first emission such thata combination of the first and second emissions at least approximatesthe target chromaticity; selecting a conversion material based on thedetermined conversion characteristic; and forming the conversionmaterial on the second semiconductor material via at least one of metalorganic chemical vapor deposition, molecular beam epitaxy, liquid phaseepitaxy, hydride vapor phase epitaxy, and ion implantation.
 2. Themethod of claim 1 wherein: the conversion material includes asuperlattice structure; and selecting the conversion material includesselecting at least one of a thickness and a composition of thesuperlattice structure based on the determined conversion characteristicof the second emission.
 3. The method of claim 1 wherein: the conversionmaterial includes a superlattice structure; and selecting the conversionmaterial includes: determining a bandgap energy that corresponds to thedetermined conversion characteristic of the second emission; andselecting at least one of a thickness and a composition of thesuperlattice structure based on the determined bandgap energy.
 4. Themethod of claim 1 wherein: the conversion material includes asuperlattice structure; and selecting the conversion material includes:determining a bandgap energy that corresponds to the determinedconversion characteristic of the second emission; selecting at least oneof a thickness and a composition of the superlattice structure based onthe determined bandgap energy; and adjusting at least one of thethickness and the composition of the superlattice structure based on thetarget chromaticity of the light emitting device.
 5. The method of claim1 wherein: the conversion material includes an epitaxial bulk materialwith a dopant of europium (Eu) and/or erbium (Er); and selecting theconversion material includes adjusting at least one of a composition anda concentration of the dopant based on the target chromaticity of thelight emitting device.
 6. A method for manufacturing a light emittingdevice, comprising: forming a first semiconductor material, an activeregion, and a second semiconductor material on a substrate material insequence, the active region being configured to produce a firstemission; forming a conversion material on the second semiconductormaterial, the conversion material having a crystalline structure andbeing configured to produce a second emission; and adjusting acharacteristic of the conversion material such that a combination of thefirst and second emission has a chromaticity at least approximating atarget chromaticity of the light emitting device.
 7. The method of claim6 wherein: the conversion material includes a superlattice structure;and adjusting the characteristic of the conversion material includesadjusting at least one of a thickness and a composition of thesuperlattice structure based on the target chromaticity of the lightemitting device.
 8. The method of claim 6 wherein: the conversionmaterial includes an epitaxial bulk material with a dopant of europium(Eu) and/or erbium (Er); and adjusting the characteristic of theconversion material includes adjusting at least one of a composition anda concentration of the dopant based on the target chromaticity of thelight emitting device.
 9. The method of claim 6 wherein: the conversionmaterial includes a semiconductor material configured as multiplequantum wells; and adjusting the characteristic of the conversionmaterial includes adjusting at least one of a composition and athickness of the multiple quantum wells based on the target chromaticityof the light emitting device.